Patent GB-233467-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-02-26
Abstract: 233,467. Coventry Automatic Telephones, Ltd., Collyer, J. E., and Wilman, C. W. Feb. 26, 1924. Automatic exchange systems; metering.-In a forward loop dialling system the line relay at the distant end of a junction is fed with current by separate back bridge relays at the originating end adapted to respond to supervisory signals sent back over either or both of the line wires. These back bridge relays are provided at transmission bridges and are used for the repetition in a. backward direction of supervisory signals or conditions, such as those for metering, for suppressing metering on a call to an operator, for allowing an operator to hold a connection or to subsequently meter any number of times, or for giving a busy flash signal to an operator. All the operations may take place over two-wire junctions between two or more serially related exchanges. In the system described, a call to a, distant exchange is extended over a first selector, Fig. 2, a second selector, Fig. 3, a two-wire inter exchange junction 201, 202, an incoming selector, Fig. 4, and a final selector, Fig. 5. Forward loop dialling is employed only between switches at different exchanges, impulses being repeated between switches in the same exchange. over one line wire, but the impulses may, if desired, be repeated between switches in the same exchange over forward loops. An operator's position, Fig. 7. is reached from certain levels of the incoming selector, Fig. 4. In applying the invention to systems employing register controllers or translators the first transmission bridge and the means for controlling the metering circuit may be incorporated in a relay group associated with the first selector trunk Call to an automatic subscriber: first group selector, Fig. 2. This is taken into use over a normal line switch similar to that described in Specification 224,692. The line relay 51 energizes the release relay 52 and earths the private, wire 24, thereby closing a circuit for a slow release relay 57, which applies dialling tone over the transformer 101. The first series of impulses operates the vertical magnet 60, and at the first step the stepping magnet 54 energizes over the offnormal springs 77, and locks up over the rotary interrupter springs 76. On the cessation of these impulses, the change-over relay 53 (energized during impulsing) relapses, and closes a circuit for the rotary magnet 61 which breaks the holding circuit of the stepping relay 54, which in turn deenergizes the rotary magnet 61. If the trunk engaged by the wipers is busy, the relay 54 energizes over the test wiper 95, locks up, and again energizes the magnet 61, which advances the wipers another step, and de-energizes the relay 54. This operation continues until an idle trunk 96 - - 93 is engaged, when the switching relay 55 energizes, cuts off the dial tone, and connects back bridge relays 58, 59 to the trunk conductors 96, 97. Second group selector, Fig. 3. The line relay 151 is energized over the lower talking conductor 97 in series with the back bridge relay 59, and the change-over and stepping relays 152, 154 energize over the private wire 98. The second series of impulses is repeated at armature 63, Fig. 2, to the line relay 151, and the vertical magnet 156 steps the wipers to the required level. At the end of the impulses, the stepping relay 154 locks up over the rotary interrupter springs 171, and the change-over relay 152 (which during impulsing is maintained energized over armature 168) relapses and completes a circuit for the rotary magnet 155, which interacts in known manner with the stepping relay 154 until an idle interexchange junction 201, 202 is engaged, when the switching relay 153 responds, extends the connection to the engaged junction, and opens the circuit of the line relay 151. The line relay 151 instead of being connected to the lower conductor only, may be bridged across the trunk 96, 97 at two sets of back contacts of the relay 153, dialling then taking place over a, forward loop including the windings of both relays 58, 59. Incoming group selector, Fig. 4. An initial circuit is closed over relay 59, Fig. 2, and the lower talking conductor for line relay 203, which energizes relays 210, 207. Relay 207 applies dialling tone from the transformer 229, opens the initial circuit of relay 203 and completes a forward loop circuit including the windings of the back bridge relays 58, 59, which respond but are ineffective at this stage. The impulses comprising the third digit are now repeated by the line relay 51, Fig. 2, to the relay 203, the relay 53 responding during impulsing and short-circuiting relay 58, to improve the impulsing circuit. The incoming group selector operates in a manner similar to the first group selector, Fig. 2, to seize an idle trunk 215 - - 217 to a final selector, the response of the switching relay 208 connecting back bridge relays 205, 206 to the upper and lower trunk conductors 215, 216. Final selector, Fig. 5. Earth on the private wire 217 energizes relay 316, which closes a circuit over the rotary off-normal springs 334 for relay 323, which completes a circuit over back bridge relay 206, Fig. 4, and the lower talking conductor for the line relay 315. Relay 315 energizes change-over relay 322. The tens impulses are repeated at armature 225 of the relay 203, Fig. 4, to relay 315, Fig. 5, which completes a stepping circuit 328, 327, 348 for the vertical magnet 326. The change-over relay 322 is maintained during impulsing over armatures 332, 333, 336, but at the end of the impulses relapses, and extends the stepping circuit to the rotary magnet 325 which in response to the units impulses steps the wipers to the wanted line. During the units impulses, the relay 323 is maintained over armatures 332, 333, 336, 335, but on their cessation it relapses and de-energizes relays 206 and 315. Busy test, signal and release. If the wanted line is busy, earth over the test wiper 345 is connected to test relay 321 before the relay 323 falls away, and on the relapse of relay 323, the relay 321 (which is rendered slow-ta-release by a non- inductive parallel winding), remains energized over contacts 328, 329, 330. Relay 321 connects alternate intermittent busy tone and busy flash current via the interrupter 349 to the upper talking conductors, and when the calling party hangs up on hearing the busy tone release occurs in known manner. Ringing. If the wanted line is idle, when relay 323 restores, the switching relay 320 locks energized, opens the circuit of relay 316, and completes a ringing circuit from the generator 351. Battery at the contacts 319 may be fed through a ringing tone coil over the upper talking conductor to give the calling party a ring back signal. When the called party answers, ringing current is cut off by the relay 314. Metering. When the switching relay 320 is energized a meter preparing condition is brought about in which the back bridge relays 58, 205 connected to the upper conductor are energized, and the back bridge relays 59, 206 connected to the lower conductor are inert. This takes place as follows. The relay 320 closes a circuit over the upper conductor for relay 205, Fig. 4, which de-energizes relay 207 which at contact 221 removes a shunt from relay 204, the impedance of which is inserted in series with line relay 203 to improve the talking circuit. A circuit 218, 219, 220, 204 is completed over the upper conductor for relay 58 which remains operated, but the battery at armature 219 forms a low-resistance shunt for relay 59, which falls away, and de-energizes relay 57. The relay 56 now prepares the metering circuit at armature 85. When the called party answers, both back bridge relays 205, 206 energize over the called loop, the relay 206 removing the shunt from relav 59, which now energizes in series with relays 203, 204, 58. The relay 57 again energizes, completes the metering circuit 24, 82, 85, 86 over the metering conductor 25, and de-energizes the slow release, relay 56, which after a short interval opens the metering circuit at armature 85. Release. This takes place in the usual manner on the relapse of the line relay 51, Fig. 2, when the calling party hangs up. Transmission of busy flash signal over the twowire junction 201, 202. If the junction 201, 202 is taken into use by an operator and the called line is found busy, each time battery is connected to the upper conductor via the interrupter 349, Fig. 5, the back bridge relay 205, Fig. 4, energizes, de-energizes relay 207, and a busy flash signal is repeated over the upper junction wire 201 over a circuit 218, 219, 220, 204. In the case of a call from an automatic subscriber, the busy flash current has no effect on the metering circuit. On the first battery impulse, relay 158 disconnects relay 57 and relav 56 operates, but at the succeeding earth period the relay 58 relapses and opens the metering circuit at armature 82 before the relay 59 again pulls up and closes the metering circuit. Call to an operator's position, Fig. 7. This position is reached over a certain level of the incoming selector. Fig. 4, and the connection proceeds in the same manner as already described for an automatic call up to the energization of the switching relay 208, when a series circuit is completed over the upper conductor for relay 205, Fig. 4, and relay 452, Fig. 7. This brings about the meter preparing condition as previously described, in which the back bridge, relays 58, 205 are energized and the back bridge relays 59, 206 are inert. Relay 452 energizes relay 454 and lights a calling lamp 461. When the operator inserts the answering plug, the sleeve relay 453 extinguishes the lamp 461, and opens the circuit of relays 452, 205. the former of which de-energizes relay 454. The relay 206, Fig 4, is also euergized over the lower conductor in series with a supervisory relay 464, Fig. 7. Thi